This invention relates to an engine management system and more particularly to a system for pumping drains from a two-cycle crankcase compression engine under some running conditions and returning them to the combustion chamber and associated controls therefor.
It is well known that with two-cycle crankcase compression engines, there is a tendency for fuel and/or lubricant to condense in the crankcase chamber or some other low portion of the engine. This accumulated liquid, at times, again becomes vaporized and mixes with the fuel that is delivered to the combustion chamber. This fluctuating amount of return of condensed liquids can give rise to rough engine performance. This problem is particularly acute in conjunction when running under low speeds and low load conditions.
Various arrangements have been proposed for draining the liquids that so accumulate in an engine and returning them to the engine induction system for burning and discharge of the burnt products to the atmosphere. Many of these systems operate on a gravity principle and thus the actual control of the timing and the volume of condensed liquid that is returned to the engine through its induction system cannot be controlled.
It is, therefore, a principal object of this invention to provide an improved arrangement for pumping accumulated liquids from a low part of a two-cycle crankcase compression engine in a controlled manner and in such a manner that the pumped liquid will not disrupt the engine running.
It is a further object of this invention to provide an improved control system for controlling the removal of condensed liquids in the engine.
Obviously from the foregoing description it should be apparent that the return of the condensed liquids to the induction system will alter the fuel/air ratio. Devices of the type previously proposed have not been able to accommodate and adjust the air/fuel ratio in response to the return of these liquids to the engine through its induction system.
This problem can be best understood by reference to FIGS. 1 and 2, which are graphical views of watercraft velocity and fuel/air ratio with respect to time in a watercraft powered by a two-cycle crankcase compression internal combustion engine upon acceleration. The solid line curve shows an ideal situation when no drains are permitted to re-enter the engine through its induction system while the dotted line curves show the actual conditions when drain recirculation is present. As may be seen when accelerating from rest to a trowling speed, the velocity of the watercraft increases much faster and reaches the optimum speed A much quicker when drains are not present and the fuel/air ratio is maintained as desired. However, when drains are mixed with the fuel air charge, then the mixture becomes overrich and performance deteriorates.
It is, therefore, a still further object of this invention to provide an improved engine management system and control arrangement wherein the return of condensed liquids to the engine is accompanied by an appropriate adjustment in the amount of fuel supplied to the engine.
It has also been found that by changing the amount of fuel supplied to the engine immediately upon return of the liquids to the induction system and the discontinuance of the leaning of the mixture upon stopping of the return, do not give rise to smooth engine performance. That is, in order to achieve smooth engine performance it may be desirable to actually lean the fuel-air ratio before the liquids are returned and to discontinue the leaning at some time period after the return of liquids has been concluded.
It is, therefore, a still further object of this invention to provide an improved drain removal system for a two-cycle crankcase compression engine incorporating an arrangement for controlling the fuel-air ratio in response to the return of the liquids to the engine through its induction system.
It is a further object of this invention to provide an improved arrangement for controlling the fuel-air ratio, both during the time when condensed liquids are returned to the engine, but also preceding that time and immediately after the return is discontinued so as to provide smooth running.